Vehicles with a hybrid drive system in the different embodiments have, in certain driving cycles, a more advantageous exhaust gas behaviour than vehicles which are driven entirely by an internal combustion engine. They therefore become more and more important on the market.
If an electric machine is used as the supplementary driving machine, it can be used as an engine and a generator. As far as the engine function is concerned, wherein it is necessary to provide a battery for power supply purposes, it is possible to use it to start an internal combustion engine or to use it as a driving motor. When used as a generator, the electric machine is used for charging the battery, wherein the energy is obtained from the internal combustion engine or from the recovery of the kinetic vehicle energy.
Hybrid drive systems are described for example in WO 2005/073005 A1, DE 100 49 514 A1 and DE 198 18 108 A1.
From DE 199 60 621 A1 there is known a hybrid drive for vehicles with a manual gearbox which comprises a first switchable partial drive which, optionally, can be connected in respect of drive to an internal combustion engine and/or an electric machine, as well as a second switchable partial drive which, in respect of drive, can be connected to the electric machine which can be operated as an electric motor or a generator. The first partial drive comprises a first lay-shaft and an output shaft as well as six transmission stages; the second partial drive comprises a second lay-shaft and the same output shaft and comprises three transmission stages.